1. Field of the Invention
The invention concerns an energy converter system mounted in a wheel hub and a process for its operation.
2. Description of the Prior Art
From DE 30 43 269 A1 a side-mounted dynamo for bicycles is known that is characterized by the integration of power electronics and an accumulator into the dynamo housing. Switching on and off of the dynamo is accomplished by manually moving the friction wheel. The mechanical on and off switch of the dynamo is required because the dynamo generates losses when idling. The transformer between the current generator and the accumulator is designed as diode circuit.
DE-PS 933 040 describes a homopolar dynamo operated as generator and designed as external rotor that is arranged without a gear in the wheel hub of bicycles and motorcycles. Homopolar machines are separately excited machines in which the exciting magnetic field is preferable generated by permanent magnets. Permanent magnet generation causes a strong cogging effect.
DE 43 17 817 C1 describes an AC-dynamo with permanent magnets in the rotor where the stator of the dynamo consists of three mutually offset induction coils with pole finger cages of soft magnetic iron. The electric machine is to run continuously as charging generator. However, the permanent magnets generate noticeable magnetic losses in the non-laminated pole fingers of the stator.
DE 44 11 145 A1 also describes a generator with identical induction coils which, however, does not have offset phases and is parallel switched in order to increase reliability of operation. The rotor with the permanent magnets is directly attached to the wheel. In order to generate sufficient power for lighting at low speeds (rpm), the generator requires considerable weight and volume. Furthermore, permanent magnetic losses in the stator iron are generated in this design also.
A smaller size is achieved by transmission gears that increase rpm. Gear dynamos in the wheel hub are known from JP 3-258 673 A or EP 0528 347 A1. Planet gears, however, are expensive and in addition increase operating resistance.
Another well-known alternative is represented by generators with air core windings in the wheel hub as described in DE 37 03 523 C2 (DC disc armatures), DE 39 18 166 C2 (EC disc armatures), or DE 42 34 388 A1. Air core windings enlarge the magnetically effective air gap and, therefore, cause high magnet expenditures.
In accordance with DE 42 32 182 A1, a brushless single phase rotor is also equipped with permanent magnets and idling losses in the core are to be reduced by a rotation of the two magnet rings in relation to each other. Idling losses are otherwise avoidable only by mechanical separation of the rotor from the wheel.
A reduction of weight can be achieved by an increase of the generator diameter in the wheel hub. Designs in this regard are known, among others, from DE-OS 27 27 827, DE 42 29 457 A1 or DE 42 29 261 C1. Here, a low degree of protection from dust and moisture and high magnet costs are disadvantages.
In DE 42 29 261 C1 the generator is designed for so much power that it can provide a noticeable contribution to driving power even in motorized operation. For motorized operation an accumulator is provided that is attached to the bicycle frame. This system is too heavy and to expensive for normal lighting purposes.
DE 43 14 290 A1 describes a switched reluctance machine and a process for control in generator operation. This is a complex, multi-phase design of a machine functioning in accordance with the reluctance principle.
From DE 195 47 159 A1 a transverse flux machine with a special air gap arrangement is known which is also executed as a switched reluctance machine. The soft magnetic body consists of numerous laminated segments which requires high assembly expenditures. In a variant of the design integrated in the wheel hub the rotor is equipped with permanent magnets.
The objective of the present invention is to advance an energy converter system integrated into the wheel hub in such a manner that a small design size and weight, high efficiency, and reliable current supply in all operation ranges is achieved at low production costs.